A strut-type suspension used for a front wheel of an automobile has structure in which a strut assembly comprising a piston rod and a hydraulic shock absorber is combined with a coil spring. When a steering is operated, the strut-type assembly is rotated together with the coil spring. Accordingly, to allow smooth rotation of the strut assembly, usually a bearing is placed between an upper mount which is a mounting mechanism for mounting the strut assembly onto the automobile body, and an upper spring seat as a spring seat for the upper end of the coil spring.
For example, the Patent Literature 1 discloses a slide bearing made of synthetic resin as a bearing for a strut-type suspension. This slide bearing comprises: an upper case made of synthetic resin which is fitted on the side of an upper mount; a lower case made of synthetic resin which is fitted on the side of an upper spring seat and combined rotatably with the upper case; and a center plate which is placed in an annular space formed by combining the upper case with the lower case and functions as a bearing body for realizing smooth rotation between the upper case and the lower case. Here, in a bearing surface of the center plate, a plurality of grooves functioning as lubricating grease reservoirs are formed, and are filled with lubricating grease. On the outer periphery side of the annular space, an outer elastic seal member is placed to close up a gap between the upper case and the lower case. Similarly, on the inner periphery side of the annular space, an inner elastic seal member is placed to close up a gap between the upper case and the lower case.
According to the synthetic-resin slide bearing described in the Patent Literature 1, since the annular space formed by combining the upper case with the lower case is sealed by the outer elastic seal and the inner elastic seal, it is possible to prevent intrusion of dust, muddy water or the like even under extreme conditions. Thus, it is possible to prevent effectively degradation of the sliding performance due to intrusion of dust, muddy water or the like between the bearing surface of the center plate placed in the annular space and a support-target surface of the upper case or the lower case facing the bearing surface.